Piezoelectric ignition mechanism

ABSTRACT

A piezoelectric ignition mechanism which produces a series of voltage surges so as to create a series of sparks across spaced terminals rather than a single spark upon impacting a piezoelectric crystal. This result is attained by using a buffer which causes the crystal to reverberate.

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sparks across spaced terminals rather than a single spark upon impactinga piezoelectric crystal. This result is attained by using a bufi'erwhich causes the crystal to reverberate.

20 l III/Ill] PATENTED APR27 zen SHEET 2 [1F 2 INVENTOR 5 1 00 4 4s ,8;F0445? //z/// A 441v; BY j W MM] ATTORNEY l PIEZOELECTRIC IGNITIONMECHANISM v BACKGROUND OF THE INVENTION It is a well-known phenomenonthat certain crystals such as quartz and some ceramics have the propertyof producing a potential difference across the faces of the crystal whenthe latter is stressed. It is also known that a higher voltage can beproduced by applying an impact force rather than a steady compressiveforce to the crystal.

By applying an impact force to a crystal, a spark can be made to jump agap between two electrodes which are connected across the faces of thecrystal by leads. Thus, one electrode is at a negative and the otherelectrode is at a positive potential. This effect has been used in anumber of articles such as a cigarette lighter or internal combustionengine for example. A gas, such as butane, is timed to pass between theelectrodes when the piezoelectric crystal is struck. When the sparkjumps the gap between the electrodes it ignites the hutane gas, and theissuing flame can be used to light a cigarette or fire a combustiblemixture in a gas cylinder. In the prior art, only one spark jumped thegap, therefore, if the gas did not ignite on the first attempt, theoperation had to be repeated. It has been shown that it takes time forthe crystal to recover in order to produce a second voltage across theelectrodes which is equal to the first. If one continues to strike thecrystal each subsequent impact products a lower voltage and aproportionately less chance of igniting the gas.

SUMMARY OF THE INVENTION This invention has greatly improved the priorart piezoelectric devices by utilizing an impact mechanism which permitsa series of sparks to be produced across the electrode gap with only oneimpact. The series of sparks greatly increases the chances ofsuccessfully igniting the gas issuing between the electrodes.

In the improved arrangement of this invention, the piezoelectric crystalis supported in a mounting which is so constructed and proportioned thatit will reverberate when the crystal is struck. The crystal is struck insuch a manner that the timing of the reverberations in the mounting willbe related to those in the crystal so as to induce a series of strongvoltage oscillations whereby to extend the time during which currentflows between the electrodes forming a spark gap; thereby, providingmore reliable ignition, because the probability that ignition will occurhas been increased.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of thepresent invention, reference may be had to the accompanying drawings inwhich:

'FIG. 1 is a side view showing parts in section;

FIG. 2 is an end view showing parts in section;

FIG. 3 is a side view showing the details of the cartridge impactmechanism;

FIG. 4 is an end view showing the details of the cartridge impactmechanism;

FIG. 4a is a detail showing the buffer mechanism;

FIG. 5 is a side view with a portion cut away showing the impactmechanism in actuated condition;

FIG. 6 is an end view with parts cut away showing the impact mechanismin actuated condition;

y FIG. 7 is a modification of the device shown in FIG. 1; and

FIG. 8 is a perspective of an end plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT disclosed herein is adapted tobe used with any mechanism for producing a spark.

The lighter shown comprises a sheath 11 which fits over and retains inoperative position the working components of the lighter. A fuelreservoir 12 is mounted within the confines of mounted within the socket14. The inlet valve can be any I known inlet valve, for example, thevalve shown in US. Pat. No. 3,085,601 which issued on Apr. 16, I963. Aflange 16 having upstanding walls 17 thereon is formed outwardly of thefuel reservoir 12 to form a receiving means for structure to be fullydisclosed hereinafter.

A fingerpiece 18 is attached to a support 19 having depending legs 20thereon. The depending legs 20 are axially aligned above a lever 21which has one end fixed to the movable stern 13a on the burner valve.The lever has a finger 22 thereon which functions as a fulcrum in whichthe finger 22 rests on the top wall of the fuel reservoir 12. The burnervalve is of the type having a movable stem 13a although any othersuitable valve can be used. When the stem 13a is raised the valve isopened and gas flows. The stem 13a is held in closed position by aspring (not shown) mounted within the valve housing. To open the burnervalve and thereby permit gas to flow, the fingerpiece I8 is depressedand the depending leg 20 contacts the end of the lever 21 which isrotated about the fulcrum 22. Since the end of the lever is attached tothe stem 13a of the burner valve, the stem is lifted and fuel containedin the reservoir 12 can flow to the atmosphere.

The fingerpiece 18 also functions to actuate the ignition mechanism 23.This is accomplished by fixing a housing 24 to the fingerpiece 18. Thehousing is preferably tubular in construction, however, any desiredshape can be used. The housing 24 has a coiled spring 25 attachedtherein which can be compressed within the housing 24. The support 19has notches 19a formed therein for the reception of a pair of opposedstruts 26 which can be in the form of U-shaped wire members. The struts26 are flexible parallel members and each set is biased inwardly towardsthe other set. The struts are firmly held in place by being clampedbetween the fingerpiece 18 and the support 19 as shown in FIG. 4.

A tubular housing 27 having opposed ends 28 and 29 which are peened overis loosely received within the walls 17 and rests on the flange 16. Thehousing 27 contains a piezoelectric crystal firmly held in a housing 30.The crystal is encapsulated in a cartridge having an anvil 31 protrudingtherefrom. Connected to the opposed faces of the crystal is a lead wire32 which terminates in an electrode 33 mounted in an insulated member33a which can be a ceramic or a plastic for example. The anvil 31extends through an opening in the crystal housing 30. The anvil 31 whichabuts the encapsulated crystal extends downwardly beyond the confines ofthe encapsulated crystal housing 30. The anvil 31 is preferably made ofmetal which enables it to withstand the impact imparted to it by ahammer 35. The hammer 35 is also preferably metallic and of relativelyhigh density. The hammer 35 is slidably received within the housing 27.The hammer can be seen through an opening 36 in the housing 27. A boss37 having a flange 38 thereon is fixed to the lower portion of thehousing 27. A coiled spring 39 fits around the boss 37 and bears on theflange 38 integral with the boss 37. A bore 40 is countersunk in thehammer 35 and receives the opposite end of the coiled spring 39. Thus,the hammer 35 is maintained firmly against the anvil 31 by the bias ofthe spring 39. A notch 41 is formed in the hammer 35 adjacent the upperportion thereof. The bight 26a of the U- shaped strut 26 fits within acorresponding opposed notch 41 in the hammer 35. The cutout portion 36of the housing 27 gradually tapers outwardly and forms a cam surface 42.When the fingerpiece 18 is depressed, the struts 26 which are located inrecesses 41 move the hammer 35 downwardly against the bias of the spring39. The struts 26 are cammed out of the the sheath 1]. The walls formingthe fuel reservoir can be notches 41 by the cam surface 42 after thehammer 35 has travelled approximately three-eighths to one-half inch.When the struts are removed from the notches, the hammer is acceleratedinto an impact engagement with the anvil 31. Upon release of thefingerpiece 18, the spring 25 returns the fingerpiece with the struts 26affixed thereto to its rest position. The bight 260 on each of thestruts thereby reengages in its respective notch 41 because the strutsare flexibly urged inwardly towards each other.

A series of elements which can be metallic and can be in the form ofwashers 56 or solid wafers 57 or a solid member 55 is placed above thecrystal housing 30. A combination of washers and wafers can also beused. A solid end plate 55 can -be also used either alone or incombination with washers and/or wafers over which the end of the housing27 is peened. The effect of placing a solid plate or washers and/orwafers ad jacent the encapsulated crystal 30 is to create a series ofsparks which increases the probability of an ignition occurring.

in the normal arrangement where the crystal is energized by impact, theaction of striking the crystal produces only one positive and onenegative voltage surge at the live electrode of very brief duration. Thebrevity of the resulting discharge frequently fails to cause ignition.The number of washers and/or wafers or the thickness of the solid memberis chosen so that the reverberations in the crystal and the washer-waferassembly resulting from the impact of the hammer 35 interact to producethree or four voltage peaks occurring in about I microseconds from thefirst impact.

in another embodiment of the invention, the encapsulated crystal in itshousing 30 is held by a block 47. The block can be received within acigarette lighter housing or in any other environment generally shown bydashed lines in FIG. 7. The

block 47 has an opening 48 therein which is dimensioned to receive thecrystal housing 30. The lead wire 32 from the crystal can be snakedthrough a bore in the block and then it terminates in an electrode 33.The electrode extends through an insulating member 49 which can be madeof any known insulating material.

A solid end plate 50 which is preferably metallic-however. any materialcan be used-is forced into the upper portion of the opening 48 so as toexert a compressive force against the crystal assembly. The plate 50 canbe given a slight chamfer along one side to provide a lead-in and theslot in the block 47 is dimensioned so that the plate 50 is a forced fittherein. Thus, when the crystal assembly and plate are locked inposition by forcing the plate into the opening 48, the crystal issubjected to a compressive force.

A very satisfactory output has been made in practice by making the plate50 and block from brass with a wall thickness not less than 0.08 inch.

The end plate 50 can be formed with a pair of outward extensions 51 sothat better reverberation characteristics can be imparted to the crystalfrom the end plate 50 which is shaped like a bridge.

A hammer 52 having a head 53 thereon is pivoted by means of a pin 54 tothe block 47. Any known mechanism can be used to place the hammer undertension and then release the latter to strike the crystal as detailed inthe first embodiment of this invention.

it is possible that, instead of using a separate solid member or washersor wafers, the end of the crystal unit could bear against a fingerlikeportion formed integrally with the housing and dimensioned to have therequired reverberation characteristics.

The flame which is produced can be adjusted by a knob 43 which, by meansof a bushing 44, is connected such as by splines to the burner valve.Since the burner valve is not part of this invention further detail isconsidered to he superfluous. A closure 45. having an opening 46 thereinfor the inlet valve l5, closes the lower portion of the lighter andretains the elemenu therein.

"To operate the ignition mechanism, the fingerpiece I8 is depressed, andsince the struts 26 are connected to the fingerpiece, they are moveddownwardly also. The struts, which are resiliently biased inwardlytowards each other have a bight portion 26a which fit within arespective notch 41. As the fingerpiece 18 is depressed, energy isstored in the spring 39 and when the struts 26a reach the cam portion 42of the housing 27 they are biased outwardly away from each other therebyremoving them from the notches. The downward movement of the fingerpiece18 also causes the leg 20 to tilt the lever 21 about its fulcrum 22 andthereby open the valve to cause gas to flow past the electrode 33.

When the hammer 35 is suddenly released by removing the restraint of thestruts 26a, the energy stored in the spring 39 will force the hammer tostrike the anvil 31. Since the anvil is in contact with thepiezoelectric crystal, a potential difference appears across the facesof the crystals. The electrode 33 is connected to one face of thecrystal and the other electrode is grounded. Since the burner valve 13ais at ground potential, it forms the other electrode and a series ofsparks will jump the gap between the electrode 33 and the burner valve13a to thereby ignite the gas emanating from the burner valve.

Although the exact mode of operation of the ignition device is not fullyunderstood, it is believed that the operation may be described asfollows: the action of striking one end of the crystal produces a shockwave which travels through the crystal and causes the plate 50 to bedeflected away from the other end of the crystal. The crystal alsocontracts to produce,

- for example, a positive-going voltage peak at the live electrode 33.The crystal then expands to produce a negative-going voltage peak, afterthis the plate 50, reverting to its norrnai position, strikes theadjacent end of the crystal which again contracts to produce apositive-going voltage peak and then expands to produce a negative-goingvoltage peak. The reverberations in the crystal and plate may continuebut subsequent voltage peaks may not have sufficient amplitude toproduce a discharge.

The energy available at the spark gap is increased considerably in theignition units according to the present invention. in mechanisms of theprior art only the energy of the initial two voltage peaks is usuallyavailable as energy for ignition at the spark gap whereas in thearrangement of the present invention, the first four peaks at least areeach effective to produce a discharge.

We claim:

1. A mechanism for creating an electrical discharge comprising:

a. a piezoelectric crystal mounted on a support,

b. an impact means for striking said piezoelectric crystal mountedadjacent said crystal so as to induce a primary voltage,

c. electrical leads connected to said crystal and terminating in a pairof electrodes forming a spark gap,

d. a buffer means mounted adjacent said crystal to induce secondaryvibrations of said crystal whereby said crystal will produce secondaryelectrical discharges subsequent to being struck by said impact meansand upon reaction with said buffer means.

2. A mechanism for creating an electrical discharge as defined in claim1 further characterized in that said buffer comprises at least onedisc-shaped member.

3. A mechanism for creating an electrical discharge as defined in claim2 further characterized in that said discshaped member has an openingtherein.

4. A mechanism for creating an electrical discharge as defined in claim1 further characterized in that said buffer comprises a relativelythick, solid end plate.

5. A mechanism for creating an electrical discharge as deiineti in claim4 further characterized in that said end plate has extensions onopposite ends thereof forming a bridge shape. m

6. A mechanism for creating an electrical discharge as defined in claimI further characterized in that said impact means comprises a hammerwhich is urged against piezoelectric crystal by a spring.

7. A mechanism for creating an electrical discharge as defined in claim1 further characterized by a first housing enclosing said piezoelectriccrystal and said impact means are in axial alignment and are finnly heldwithin said first housing.

8. A mechanism for creating an electrical discharge as defined in claim7 further characterized in that said buffer is mounted within said firsthousing between said crystal and the top portion of the first housing.

9. A mechanism for creating an electrical discharge as defined in claim7 further characterized in that a second housing is telescopicallyreceived over said first housing, in which a fingerpiece is fixed tosaid second housing, means on said fingerpiece which engages said hammerand depresses it against the bias of the spring and releases said hammerafter a predetermined amount of energy is stored in said spring.

10. A mechanism for creating an electrical discharge as defined in claim1 further characterized in that said first housing is a block having anopening therein for the reception of said crystal.

11. A mechanism for creating an electrical discharge as defined in claim10 further characterized in that said hammer is pivotally attached tosaid block and the hammerhead is in axial alignment with said crystal soas to strike the latter.

12. A mechanism for creating an electrical discharge as defined in claim1 further characterized in that a fuel reservoir is adjacent saidcrystal, said fuel reservoir has a burner valve mounted on one endthereof, a fingerpiece mounted on said support to actuate the burnervalve and the impact means, an electrode mounted adjacent said burnervalve and electrically connected to said crystal such that uponactuation of 'said impact means, a spark ignites the gas emanating fromsaid burner valve.

13. A mechanism for creating an electrical discharge as defined in claim1 further characterized by a fuel reservoir mounted adjacent saidcrystal and having a flange thereon upon which said crystal is received.

Patent No. 3,576 ,383 Dated April 27, 1971 Inventor(s) Douglas S.Fuller; g Lang It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

On the cover page of the application in the heading of the patent thename of the Assignee should read Ronson Corporation.

Signed and sealed this L .th day of July 1972.

(SEAL) Attest:

LDWARD M.FLETCHR, JR ROBERT GOTTSCHALK Attesting Officer CommissioneroiPaten

2. A mechanism for creating an electrical discharge as defined in claim1 further characterized in that said buffer comprises at least onedisc-shaped member.
 3. A mechanism for creating an electrical dischargeas defined in claim 2 further characterized in that said disc-shapedmember has an opening therein.
 4. A mechanism for creating an electricaldischarge as defined in claim 1 further characterized in that saidbuffer comprises a relatively thick, solid end plate.
 5. A mechanism forcreating an electrical discharge as defined in claim 4 furthercharacterized in that said end plate has extensions on opposite endsthereof forming a bridge shape.
 6. A mechanism for creating anelectrical discharge as defined in claim 1 further characterized in thatsaid impact means comprises a hammer which is urged againstpiezoelectric crystal by a spring.
 7. A mechanism for creating anelectrical discharge as defined in claim 1 further characterized by afirst housing enclosing said piezoelectric crystal and said impact meansare in axial alignment and are firmly held within said first housing. 8.A mechanism for creating an electrical discharge as defined in claim 7further characterized in that said buffer is mounted within said firsthousing between said crystal and the top portion of the first housing.9. A mechanism for creating an electrical discharge as defined in claim7 further characterized in that a second housing is telescopicallyreceived over said first housing, in which a fingerpiece is fixed tosaid second housing, means on said fingerpiece which engages said hammerand depresses it against the bias of the spring and releases said hammerafter a predetermined amount of energy is stored in said spring.
 10. Amechanism for creating an electrical discharge as defined in claim 1further characterized in that said first housing is a block having anopening therein for the reception of said crystal.
 11. A mechanism forcreating an electrical discharge as defined in claim 10 furthercharacterized in that said hammer is pivotally attached to said blockand the hammerhead is in axial alignment with said crystal so as tostrike the latter.
 12. A mechanism for creating an electrical dischargeas defined in claim 1 further characterized in that a fuel reservoir isadjacent said crystal, said fuel reservoir has a burner valve mounted onone end thereof, a fingerpiece mounted on said support to actuate theburner valve and the impact means, an electrode mounted adjacent saidburner valve and electrically connected to said crystal such that uponactuation of said impact means, a spark ignites the gas emanating fromsaid burner valve.
 13. A mechanism for creating an electrical dischargeas defined in claim 1 further characterized by a fuel reservoir mountedadjacent said crystal and having a flange thereon upon which saidcrystal is received.